Surface acoustic wave (SAW) applications for signal processing and other requirements often utilize a simple compact high performance SAW multiplier for use in sorting out different frequencies. for example, in receivers in which individual channels overlap on contiguous frequencies, or in data transmission in which case the channels are discrete. While the multiplexer must have good frequency sorting capabilities, it should also have wide bandwidth and low insertion loss. In addition, the device should be easy to construct and implement.
The SAW multiplexer of the present invention is a simple compact, high performance multiplexer by the use configuration using a tapered transducer and matching pickup electrodes. The device of the present invention utilizes a surface transducer of a specially constructed form. The transducer has hyperbolically tapered fingers and is constructed in a manner similar to that shown in U.S. Pat. No. 4,635,008, which was invented by the inventor of the present invention, and is assigned to the assignee of the present invention. U.S. Pat. No. 4,635,008 is hereby incorporated-by-reference into this document.
The transducer of this patent has a number of hyperbolically tapered interdigital fingers which are separated from each other in such a manner that the frequencies launched by the transducer or are received by the transducer, vary from high frequencies at one end of the transducer where the electrode fingers are closely spaced together, to lower frequencies at the opposite end of the transducer where the fingers are more widely separated. The surface acoustical waves that are, therefore, launched by this transducer vary in a like manner as they travel across the surface of the SAW conducting crystal.